A simple example I could recall from the other day is something like this:

  export type LinkedWorksheetsRecord = Record<WorksheetId, Record<WorksheetId, ReferenceTypeId[]>>;
  export type LinkedWorksheetsMap = Map<WorksheetId, Map<WorksheetId, ReferenceTypeId[]>>;

What I would rather have written instead is however something like this:

  export type LinkedWorksheets<T> = T<WorksheetId, T<WorksheetId, ReferenceTypeId[]>>;
  ...
  const myMap: LinkedWorksheets<Map> = ...;

This is however not possible, because `Map` is a type constructor which expects two more type arguments `K, V` until it is a fully applied, concrete type `Map<K, V>`.

With a library like this, this is probably possible (unless I've missed something which wouldn't surprise me). It would unfortunately surely be more verbose.

Still, I would be against pulling in a dependency only for something like this. The above example is simple I believe, but not exactly a "killer-app". And no, Monads aren't either (if you don't limit effects and don't have do-notation) :P

Not really possible, because Record and Map aren't compatible at all. At best they both have something like `toString`. You'll need to define at least something like RecordFunctor<T> and MapFunctor<T> to make this useful.

Only if you want to abstract over them at usage-site.

In my case I only ever used the concrete types and converted between them at some point.

Oh, so it's just a type alias for readability. Then it makes sense.

Thank you for the explanation, seeing a simple concrete example really helps.